you can also do a core-i3 based build as well, game performance will be better in cpu demanding games (like guild wars 2, etc) - something I would shoot for:
If nothing else, swap out your case for the Fractal uATX it's much better, or maybe this Cougar mid-tower $35 w/ promo code & free shipping
if you don't mind a standard ATX size case not a bad deal. Had to drop to the 7770, only a very slight downgrade from the 6850 IMO (although you could ditch the DVDRW and put in the 6850 if you already have one) and good deal on the 2x4Gb Gskill Ares so that's a nice bump up for a few bux more.
Compaq 7550 - 17" CRT
it is what it is, you will get great frame rates
I gave up on the old CRTs years ago so I can barely remember - I do recall the last one I used was going bad and really fuzzy and was hurtful to look at for any extended amount of time. About $60 should get you a 19" wide screen LCD, well worth the upgrade.
Well hope this gives you some ideas, the x3 is not so bad at all however it may be a limiting factor in certain games.